These files are encoded using MPEG-1 (for the 320x240) and MPEG-2 (for the 720x480). To view the MPEG-2 files you will need the proper codec. If your PC has a DVD player, you probably have that codec already. Otherwise, try a google search for "free mpeg2 codec".
It seems browsers may have problems opening these files, so you might want to right click, then select "Save As" or "Save Target As" to save the files instead of opening them directly. Then launch them locally on your system with your viewer.